The present invention relates to a solution dispenser and more particularly to a dispenser in which preservatives and other components may be removed from a solution as the solution is dispensed. The invention also provides a method for the removal of preservatives and other components from a solution as the solution is dispensed. In one embodiment, the invention provides a dispenser and method for altering the pH of a solution or dispersion as it passes through a dispenser.
Many solutions are available for making contact lenses more comfortable, safer, and easier to wear. For example, wetting solutions facilitate the wetting of a lens, soaking solutions serve as anti-microbial storage medium and prevent dehydration and distortion of the lens, and cleaning solutions remove accumulated eye secretions and other contaminants from lenses. A large number of other solutions are also used by contact lens patients. These ophthalmic solutions are typically marketed in squeezable plastic containers or aerosol cans having a nozzle through which the solution is dispensed.
Because these solutions come in contact either directly or indirectly with the eye, it is very important that they be free of microbial growth. To this end, it is common practice for preservatives to be provided in these solutions. Among the preservatives used in ophthalmic solutions are polymoxin B sulfate, quaternary ammonium compounds, chlorobutanol, organic mercurials, p-hydroxybenzoic acid esters, and certain phenyls and substituted alcohols.
A problem exists, however, in that the preservatives used in the ophthalmic solutions can cause eye irritation if used in high concentrations. For example, benzalkonium chloride (BAK) is used as a preservative in ophthalmic solutions and has broad antibacterial and anti-fungal activity when used with other components, such as disodium ethylene diaminetetraacetic acid (EDTA). However, it has been reported that repeated use of BAK can denature the corneal protein and cause irreversible eye damage. Also, in addition to chemical sensitivity, a number of contact lens wearers have allergic reactions to the preservatives used in ophthalmic solutions, even at relatively low concentrations.
The typical remedy for overcoming chemical sensitivity and allergic reactions to preservatives in ophthalmic solutions entails switching the patients to an unpreserved solution. However, unpreserved solutions present problems in marketing, as well as in home storage, in that once the container housing the solution is opened, the solution quickly becomes contaminated and unsuitable for further use. They also tend to be very expensive to produce.
Therefore, there exists a need for an apparatus which removes preservatives, as well as other components, from a solution as the solution is dispensed to a patient.
There exists a further need for such an apparatus which is easily manufactured and economical to use.
There exists a further need for an apparatus which may be attached to a standard solution container.